In a continuing investigation of factors affecting the central nervous control of oxytocin secretion, work is underway to examine the possibility that the utero-ovarian complex may influence the secretion of oxytocin. Sheep bearing utero-ovarian transplants will serve as model animals for these experiments. Circulating progesterone, estrogen, oxytocin and prostaglandins, thought to be the critical signals in this putative control system, are being measured by radioimmunoassay. A technique for monitoring the dynamics of prostaglandin synthesis by the brain has been developed to provide a tool to study the role of centrally produced prostaglandins in the control of oxytocin secretion. Finally, animals bearing indwelling cerebroventricular cannulae are being prepared to aid in the study of the roles of both prostaglandins and biogenic amines in the regulation of oxytocin secretion. Bibliographic references: Roberts, J.S., Barcikowski, B., Wilson, L., Skarnes, R.C., and McCracken, J.A. Hormonal and related factors affecting the release of prostaglandin F2 alpha from the uterus. J. Steroid Biochem. 6: 1091, 1975.